PAN endonuclease-IN-1 (Compound 23) is a potent PAN endonuclease inhibitor, with K d values of 277 μM, 384 μM and 328 μM for WT, I38T and E23K PA N endonucleases, respectively. The RNA-dependent RNA polymerase acidic N-terminal (PAN) endonuclease , a critical component of influenza viral replication machinery, is an antiviral target.